* XViewer is a framework around JFace-TreeViewer and hence the native
SWT-Tree
* Grid is a completely custom drawn and much more flexible (it tries to
mimic XLS-Sheets) ontop of it are 2 JFace-Viewers which work like the
ones from JFace-Core

It might be a nice project to make XViewer use GridTreeViewer instead
of TreeViewer ;-)